Mercury Alert: The FDA’s List of Fish to Avoid for a Healthier Life

By Jingduan Yang

Seafood is nutrient-rich and delicious, leading the U.S. Food and Drug Administration (FDA) to recommend it as part of a healthy diet. However, it also carries health risks, mainly due to heavy metals like mercury that often exceed safe levels.

As early as October 2021, the FDA, in collaboration with the U.S. Environmental Protection Agency (EPA), issued advice on fish consumption (broadly referring to fish and other seafood) that incorporated suggestions from the 2020–2025 Dietary Guidelines for Americans. The FDA advises children (ages 1 to 11), pregnant women, those who may become pregnant, or those who are breastfeeding to consume fish with lower mercury content according to updated intake recommendations. They have identified seven types of fish with mercury levels that exceed safety standards.

Why does the FDA pay special attention to the effects of seafood on children and pregnant or breastfeeding women? Seafood is vital for both infants and children. It provides essential nutrients during pregnancy and breastfeeding that support the development of the brain, spinal cord, and immune system. However, seafood is also a major dietary source of mercury, which can harm the nervous system and pose significant health risks, particularly to infants and young children. Additionally, seafood may expose consumers to other pollutants. Therefore, these populations should choose seafood based on mercury content and control their intake accordingly.

7 High-Mercury Fish Species to Avoid

The FDA categorizes fish into three recommendation levels: “Best Choices,” “Good Choices,” and “Choices to Avoid.”

When selecting fish, the key consideration is to avoid those with high mercury levels. The FDA has identified seven types of fish with higher mercury content: king mackerel, swordfish, orange roughy, shark, marlin, tilefish (Gulf of Mexico), and bigeye tuna. These fish are listed under “Choices to Avoid,” especially for children and pregnant women.

The “Good Choices” list includes bluefish, buffalofish, carp, grouper, Chilean sea bass, halibut, white and yellowfin tuna, mahi mahi, Atlantic tilefish, and Pacific croaker.

The "Good Choices" and "Choices to Avoid," as recommended by the FDA. (Source: Food and Drug Administration) — The “Good Choices” and “Choices to Avoid,” as recommended by the FDA. (Source: Food and Drug Administration)

Pregnant women, women planning to become pregnant, and breastfeeding women should consume fish from the “Best Choices” list. These fish have lower mercury levels, which helps prevent infants from being exposed to mercury and other heavy metals through the mother’s body and breast milk.

"Best Choices" for fish consumption, as recommended by the FDA. (Source: Food and Drug Administration) — “Best Choices” for fish consumption, as recommended by the FDA. (Source: Food and Drug Administration)

The “Best Choices” list includes anchovy, Atlantic croaker, Atlantic mackerel, black sea bass, butterfish, catfish, clam, cod, crab, crawfish, flounder, herring, lobster, oysters, shad, sardine, scallop, shrimp, squid, trout, salmon, and more, with approximately 30 varieties available (see the complete list for details).

The guidelines recommend a higher seafood intake for some children. These children should consume only fish from the “Best Choices” list with lower mercury levels.

Despite the FDA’s list, it is still recommended to prioritize wild-caught fish from deep-sea fishing. Farmed fish may be subject to certain contaminants due to feed additives, environmental conditions, and soil quality.

Nutritional Benefits of Fish

In addition to being nutritious, most fish are excellent sources of protein. Additionally, most fats found in fish are healthy polyunsaturated fatty acids, including omega-3 and omega-6 fatty acids. Along with iron, iodine, and choline, these nutrients are crucial for rapid brain development in early childhood.

Fish is also an important source of selenium, zinc, and other essential minerals. Additionally, it is a natural source of various B vitamins, including vitamin B12. Oily fish, in particular, provide vitamins A and D. Iron and zinc help strengthen children’s immune systems, while choline supports the development of infants’ spinal cords.

The guidelines indicate strong evidence that fish can promote heart health as part of a healthy diet. Research also suggests that a diet rich in fish and other healthy foods can reduce the risk of being overweight or obese and lower the risks of hip fractures, colon cancer, and rectal cancer.

Contaminants in Fish: Mercury and Methylmercury

Mercury is a naturally occurring element in the environment and is also released through various human activities. It can accumulate in streams, lakes, and oceans, where it is converted into methylmercury in water or sediment. Methylmercury, a form of mercury, is found in fish and acts as a neurotoxin.

Prolonged exposure to excessive methylmercury can damage the brain and nervous system. According to the EPA, pregnant women who consume seafood containing methylmercury may expose their unborn babies to it. This exposure can adversely affect brain and nervous system development, affecting “cognitive thinking, memory, attention, language, fine motor skills, and visual spatial skills.”

Almost all fish contain at least trace amounts of methylmercury. The higher a fish is on the food chain, the more mercury it can accumulate. Top predators in the food chain, such as sharks, tend to have higher mercury levels due to their consumption of smaller fish. Additionally, as these fish age and grow larger, they accumulate more heavy metals in their bodies. Therefore, choosing smaller fish and shrimp that primarily feed on algae is advisable, as they typically have lower mercury levels.

How Much Fish Should I Eat?

To gain the nutritional benefits of fish while avoiding excessive mercury intake, what is the recommended amount of fish to consume?

According to the FDA guidelines, pregnant and breastfeeding women should consume about 4 ounces (approximately 113 grams) of fish per serving two to three times a week. Four ounces is roughly the size and thickness of an adult palm.

For children, the recommended intake varies by age as follows:

Ages 1 to 3 years: 1 ounce per serving, twice a week
Ages 4 to 7 years: 2 ounces per serving, twice a week
Ages 8 to 10 years: 3 ounces per serving, twice a week
Ages 11 and older: 4 ounces per serving, twice a week

For adults, it is recommended to consume 8 ounces (approximately 226 grams) per serving twice a week.

5 Precautions for Safe Fish Consumption

Choose a variety of fish from the “Best Choices” list rather than just sticking to a single species.
Note that mercury is present throughout fish tissues, so cleaning or cooking will not reduce its content.
Pregnant women and children are advised to avoid consuming raw fish, including sushi or sashimi, due to their weaker immune systems and higher susceptibility to foodborne illnesses.
Fish is a common food allergen. If your family has a history of food allergies or your child shows any signs of an allergic reaction, consult your child’s doctor or nurse.
Exercise caution when consuming fish caught by friends or family. Avoid overconsumption, especially of larger fish such as carp, catfish, trout, and bass. Be aware of the water quality where fish were caught and the potential mercury contamination levels to ensure safety.

Infrequent and Limited Varieties of Fish Consumption

A comprehensive study titled “The Role of Seafood Consumption in Child Growth and Development” was completed and published in May. The FDA initiated this study with the National Academies of Sciences, Engineering, and Medicine. The report revealed the following surprising findings:

Both children and pregnant women consume seafood at levels significantly below the recommended amounts.
Americans eat a limited variety of fish.
According to dietary intake data from 2018 to 2019, the top 10 seafood species consumed by the U.S. population (including salmon and tuna) accounted for approximately three-quarters of total seafood consumption.
Seafood is a rich source of vitamin D, calcium, potassium, iron, and omega-3 long-chain polyunsaturated fatty acids (n-3 LCPUFAs). N-3 LCPUFAs are essential during pregnancy, lactation, and childhood, with seafood being their primary source. Additionally, seafood provides choline, iodine, and magnesium, crucial throughout childhood and adolescence. People who do not consume seafood may have deficient intake levels of n-3 LCPUFAs. In fact, most Americans and Canadians do not meet the recommended intake levels of n-3 LCPUFAs from seafood alone.